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In-Reply-To: <20200717054615.GI2922385@builder.lan>
From:   Mathieu Poirier <mathieu.poirier@linaro.org>
Date:   Mon, 20 Jul 2020 10:44:50 -0600
Message-ID: <CANLsYkxgPgJ47mC2t1kQsV+S_O1uAwneGL5qYWLV9tVe7i3oUQ@mail.gmail.com>
Subject: Re: [PATCH v4 1/2] remoteproc: Add remoteproc character device interface
To:     Bjorn Andersson <bjorn.andersson@linaro.org>
Cc:     Siddharth Gupta <sidgup@codeaurora.org>,
        Andy Gross <agross@kernel.org>,
        Ohad Ben-Cohen <ohad@wizery.com>, Jon Corbet <corbet@lwn.net>,
        linux-remoteproc <linux-remoteproc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        tsoni <tsoni@codeaurora.org>, psodagud <psodagud@codeaurora.org>,
        Rishabh Bhatnagar <rishabhb@codeaurora.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, 16 Jul 2020 at 23:48, Bjorn Andersson
<bjorn.andersson@linaro.org> wrote:
>
> On Wed 15 Jul 13:18 PDT 2020, Mathieu Poirier wrote:
>
> > On Tue, Jul 07, 2020 at 12:07:49PM -0700, Siddharth Gupta wrote:
> > > Add the character device interface into remoteproc framework.
> > > This interface can be used in order to boot/shutdown remote
> > > subsystems and provides a basic ioctl based interface to implement
> > > supplementary functionality. An ioctl call is implemented to enable
> > > the shutdown on release feature which will allow remote processors to
> > > be shutdown when the controlling userpsace application crashes or hangs.
> > >
> > > Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>
> > > Signed-off-by: Siddharth Gupta <sidgup@codeaurora.org>
> > > ---
> > >  Documentation/userspace-api/ioctl/ioctl-number.rst |   1 +
> > >  drivers/remoteproc/Kconfig                         |   9 ++
> > >  drivers/remoteproc/Makefile                        |   1 +
> > >  drivers/remoteproc/remoteproc_cdev.c               | 146 +++++++++++++++++++++
> > >  drivers/remoteproc/remoteproc_internal.h           |  28 ++++
> > >  include/linux/remoteproc.h                         |   5 +
> > >  include/uapi/linux/remoteproc_cdev.h               |  37 ++++++
> > >  7 files changed, 227 insertions(+)
> > >  create mode 100644 drivers/remoteproc/remoteproc_cdev.c
> > >  create mode 100644 include/uapi/linux/remoteproc_cdev.h
> > >
> > > diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
> > > index 59472cd..2a19883 100644
> > > --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> > > +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> > > @@ -339,6 +339,7 @@ Code  Seq#    Include File                                           Comments
> > >  0xB4  00-0F  linux/gpio.h                                            <mailto:linux-gpio@vger.kernel.org>
> > >  0xB5  00-0F  uapi/linux/rpmsg.h                                      <mailto:linux-remoteproc@vger.kernel.org>
> > >  0xB6  all    linux/fpga-dfl.h
> > > +0xB7  all    uapi/linux/remoteproc_cdev.h                            <mailto:linux-remoteproc@vger.kernel.org>
> > >  0xC0  00-0F  linux/usb/iowarrior.h
> > >  0xCA  00-0F  uapi/misc/cxl.h
> > >  0xCA  10-2F  uapi/misc/ocxl.h
> > > diff --git a/drivers/remoteproc/Kconfig b/drivers/remoteproc/Kconfig
> > > index c4d1731..652060f 100644
> > > --- a/drivers/remoteproc/Kconfig
> > > +++ b/drivers/remoteproc/Kconfig
> > > @@ -14,6 +14,15 @@ config REMOTEPROC
> > >
> > >  if REMOTEPROC
> > >
> > > +config REMOTEPROC_CDEV
> > > +   bool "Remoteproc character device interface"
> > > +   help
> > > +     Say y here to have a character device interface for the remoteproc
> > > +     framework. Userspace can boot/shutdown remote processors through
> > > +     this interface.
> > > +
> > > +     It's safe to say N if you don't want to use this interface.
> > > +
> > >  config IMX_REMOTEPROC
> > >     tristate "IMX6/7 remoteproc support"
> > >     depends on ARCH_MXC
> > > diff --git a/drivers/remoteproc/Makefile b/drivers/remoteproc/Makefile
> > > index e8b886e..311ae3f 100644
> > > --- a/drivers/remoteproc/Makefile
> > > +++ b/drivers/remoteproc/Makefile
> > > @@ -9,6 +9,7 @@ remoteproc-y                                += remoteproc_debugfs.o
> > >  remoteproc-y                               += remoteproc_sysfs.o
> > >  remoteproc-y                               += remoteproc_virtio.o
> > >  remoteproc-y                               += remoteproc_elf_loader.o
> > > +obj-$(CONFIG_REMOTEPROC_CDEV)              += remoteproc_cdev.o
> > >  obj-$(CONFIG_IMX_REMOTEPROC)               += imx_rproc.o
> > >  obj-$(CONFIG_INGENIC_VPU_RPROC)            += ingenic_rproc.o
> > >  obj-$(CONFIG_MTK_SCP)                      += mtk_scp.o mtk_scp_ipi.o
> > > diff --git a/drivers/remoteproc/remoteproc_cdev.c b/drivers/remoteproc/remoteproc_cdev.c
> > > new file mode 100644
> > > index 0000000..8a0eb47
> > > --- /dev/null
> > > +++ b/drivers/remoteproc/remoteproc_cdev.c
> > > @@ -0,0 +1,146 @@
> > > +// SPDX-License-Identifier: GPL-2.0-only
> > > +/*
> > > + * Character device interface driver for Remoteproc framework.
> > > + *
> > > + * Copyright (c) 2020, The Linux Foundation. All rights reserved.
> > > + */
> > > +
> > > +#include <linux/cdev.h>
> > > +#include <linux/fs.h>
> > > +#include <linux/module.h>
> > > +#include <linux/mutex.h>
> > > +#include <linux/compat.h>
> > > +#include <linux/remoteproc.h>
> > > +#include <linux/uaccess.h>
> > > +#include <uapi/linux/remoteproc_cdev.h>
> >
> > Alphabetical order please.
> >
> > > +
> > > +#include "remoteproc_internal.h"
> > > +
> > > +#define NUM_RPROC_DEVICES  64
> > > +static dev_t rproc_major;
> > > +
> > > +static ssize_t rproc_cdev_write(struct file *filp, const char __user *buf, size_t len, loff_t *pos)
> > > +{
> > > +   struct rproc *rproc = container_of(filp->f_inode->i_cdev, struct rproc, char_dev);
> > > +   int ret = 0;
> > > +   char cmd[10];
> > > +
> > > +   if (!len || len > sizeof(cmd))
> > > +           return -EINVAL;
> > > +
> > > +   ret = copy_from_user(cmd, buf, sizeof(cmd));
> > > +   if (ret)
> > > +           return -EFAULT;
> > > +
> > > +   if (sysfs_streq(cmd, "start")) {
> > > +           if (rproc->state == RPROC_RUNNING)
> > > +                   return -EBUSY;
> > > +
> > > +           ret = rproc_boot(rproc);
> > > +           if (ret)
> > > +                   dev_err(&rproc->dev, "Boot failed:%d\n", ret);
> > > +   } else if (sysfs_streq(cmd, "stop")) {
> > > +           if (rproc->state != RPROC_RUNNING)
> > > +                   return -EINVAL;
> > > +
> > > +           rproc_shutdown(rproc);
> > > +   } else {
> > > +           dev_err(&rproc->dev, "Unrecognized option\n");
> > > +           ret = -EINVAL;
> > > +   }
> > > +
> > > +   return ret ? ret : len;
> > > +}
> > > +
> > > +static long rproc_device_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
> > > +{
> > > +   struct rproc *rproc = container_of(filp->f_inode->i_cdev, struct rproc, char_dev);
> > > +   void __user *argp = compat_ptr(arg);
> > > +   int ret;
> > > +   int32_t param;
> > > +
> > > +   switch (ioctl) {
> > > +   case RPROC_SET_SHUTDOWN_ON_RELEASE:
> > > +           ret = copy_from_user(&param, argp, sizeof(int32_t));
> > > +           if (ret) {
> > > +                   dev_err(&rproc->dev, "Data copy from userspace failed\n");
> > > +                   return -EFAULT;
> > > +           }
> > > +           mutex_lock(&rproc->lock);
> > > +           rproc->cdev_put_on_release = param ? true : false;
> > > +           mutex_unlock(&rproc->lock);
> > > +           break;
> > > +   case RPROC_GET_SHUTDOWN_ON_RELEASE:
> > > +           mutex_lock(&rproc->lock);
> > > +           ret = copy_to_user(argp, &rproc->cdev_put_on_release, sizeof(bool));
> > > +           mutex_unlock(&rproc->lock);
> > > +           if (ret) {
> > > +                   dev_err(&rproc->dev, "Data copy to userspace failed\n");
> > > +                   return -EFAULT;
> > > +           }
> > > +           break;
> > > +   default:
> > > +           dev_err(&rproc->dev, "Unsupported ioctl\n");
> > > +           return -EINVAL;
> > > +   }
> > > +
> > > +   return 0;
> > > +}
> > > +
> > > +static int rproc_cdev_release(struct inode *inode, struct file *filp)
> > > +{
> > > +   struct rproc *rproc = container_of(inode->i_cdev, struct rproc, char_dev);
> > > +   bool release;
> > > +
> > > +   mutex_lock(&rproc->lock);
> > > +   release = rproc->cdev_put_on_release;
> > > +   mutex_unlock(&rproc->lock);
> > > +
> > > +   if (release && rproc->state == RPROC_RUNNING)
> >
> > I think the state of the processor should also be acquired when the lock is
> > held.  There is still a chance ->state can change between the time the lock is
> > released and rproc_shutdown() is called but that's a known problem for which
> > patches have been sent out.
> >
>
> There where patches for a similar bug in the debugfs interface, but I'm
> not able to find anything for rproc_shutdown().

You are correct - I was under the impression Alex's patch was for
rproc_shutdown() as well.

>
>
> As I suggested in the previous version of this series I think it's ok
> that we move forward with replicating the same faulty logic that we have
> in the sysfs interface and then fix rproc_shutdown() so that it
> internally checks the current state and return appropriately.

I also think this is the right way to proceed.

>
> Regards,
> Bjorn
>
> > > +           rproc_shutdown(rproc);
> > > +
> > > +   return 0;
> > > +}
> > > +
> > > +static const struct file_operations rproc_fops = {
> > > +   .write = rproc_cdev_write,
> > > +   .compat_ioctl = rproc_device_ioctl,
> > > +   .release = rproc_cdev_release,
> > > +};
> > > +
> > > +int rproc_char_device_add(struct rproc *rproc)
> > > +{
> > > +   int ret;
> > > +   dev_t cdevt;
> > > +
> > > +   cdev_init(&rproc->char_dev, &rproc_fops);
> > > +   rproc->char_dev.owner = THIS_MODULE;
> > > +
> > > +   cdevt = MKDEV(rproc_major, rproc->index);
> > > +   ret = cdev_add(&rproc->char_dev, cdevt, 1);
> > > +   if (ret < 0)
> > > +           goto out;
> > > +
> > > +   rproc->dev.devt = cdevt;
> > > +out:
> > > +   return ret;
> > > +}
> > > +
> > > +void rproc_char_device_remove(struct rproc *rproc)
> > > +{
> > > +   __unregister_chrdev(rproc_major, rproc->index, 1, "remoteproc");
> > > +}
> > > +
> > > +void __init rproc_init_cdev(void)
> > > +{
> > > +   int ret;
> > > +
> > > +   ret = alloc_chrdev_region(&rproc_major, 0, NUM_RPROC_DEVICES, "remoteproc");
> > > +   if (ret < 0)
> > > +           pr_err("Failed to alloc rproc_cdev region, err %d\n", ret);
> > > +}
> > > +
> > > +void __exit rproc_exit_cdev(void)
> > > +{
> > > +   unregister_chrdev_region(MKDEV(rproc_major, 0), NUM_RPROC_DEVICES);
> >
> > Please go back to the comment I made on this during my last review and respin.
> >
> > > +}
> > > diff --git a/drivers/remoteproc/remoteproc_internal.h b/drivers/remoteproc/remoteproc_internal.h
> > > index 4ba7cb5..f091ddc 100644
> > > --- a/drivers/remoteproc/remoteproc_internal.h
> > > +++ b/drivers/remoteproc/remoteproc_internal.h
> > > @@ -47,6 +47,34 @@ extern struct class rproc_class;
> > >  int rproc_init_sysfs(void);
> > >  void rproc_exit_sysfs(void);
> > >
> > > +#ifdef CONFIG_REMOTEPROC_CDEV
> > > +void rproc_init_cdev(void);
> > > +void rproc_exit_cdev(void);
> > > +int rproc_char_device_add(struct rproc *rproc);
> > > +void rproc_char_device_remove(struct rproc *rproc);
> > > +#else
> > > +static inline void rproc_init_cdev(void)
> > > +{
> > > +}
> > > +
> > > +static inline void rproc_exit_cdev(void)
> > > +{
> > > +}
> > > +
> > > +/*
> > > + * The character device interface is an optional feature, if it is not enabled
> > > + * the function should not return an error.
> > > + */
> > > +static inline int rproc_char_device_add(struct rproc *rproc)
> > > +{
> > > +   return 0;
> > > +}
> > > +
> > > +static inline void  rproc_char_device_remove(struct rproc *rproc)
> > > +{
> > > +}
> > > +#endif
> > > +
> > >  void rproc_free_vring(struct rproc_vring *rvring);
> > >  int rproc_alloc_vring(struct rproc_vdev *rvdev, int i);
> > >
> > > diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> > > index e7b7bab..669cbfb 100644
> > > --- a/include/linux/remoteproc.h
> > > +++ b/include/linux/remoteproc.h
> > > @@ -40,6 +40,7 @@
> > >  #include <linux/virtio.h>
> > >  #include <linux/completion.h>
> > >  #include <linux/idr.h>
> > > +#include <linux/cdev.h>
> >
> > Move this above completion.h
> >
> > With all of the above modifications:
> >
> > Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> >
> > >  #include <linux/of.h>
> > >
> > >  /**
> > > @@ -488,6 +489,8 @@ struct rproc_dump_segment {
> > >   * @auto_boot: flag to indicate if remote processor should be auto-started
> > >   * @dump_segments: list of segments in the firmware
> > >   * @nb_vdev: number of vdev currently handled by rproc
> > > + * @char_dev: character device of the rproc
> > > + * @cdev_put_on_release: flag to indicate if remoteproc should be shutdown on @char_dev release
> > >   */
> > >  struct rproc {
> > >     struct list_head node;
> > > @@ -523,6 +526,8 @@ struct rproc {
> > >     int nb_vdev;
> > >     u8 elf_class;
> > >     u16 elf_machine;
> > > +   struct cdev char_dev;
> > > +   bool cdev_put_on_release;
> > >  };
> > >
> > >  /**
> > > diff --git a/include/uapi/linux/remoteproc_cdev.h b/include/uapi/linux/remoteproc_cdev.h
> > > new file mode 100644
> > > index 0000000..c43768e
> > > --- /dev/null
> > > +++ b/include/uapi/linux/remoteproc_cdev.h
> > > @@ -0,0 +1,37 @@
> > > +/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */
> > > +/*
> > > + * IOCTLs for Remoteproc's character device interface.
> > > + *
> > > + * Copyright (c) 2020, The Linux Foundation. All rights reserved.
> > > + */
> > > +
> > > +#ifndef _UAPI_REMOTEPROC_CDEV_H_
> > > +#define _UAPI_REMOTEPROC_CDEV_H_
> > > +
> > > +#include <linux/ioctl.h>
> > > +#include <linux/types.h>
> > > +
> > > +#define RPROC_MAGIC        0xB7
> > > +
> > > +/*
> > > + * The RPROC_SET_SHUTDOWN_ON_RELEASE ioctl allows to enable/disable the shutdown of a remote
> > > + * processor automatically when the controlling userpsace closes the char device interface.
> > > + *
> > > + * input parameter: integer
> > > + *   0             : disable automatic shutdown
> > > + *   other : enable automatic shutdown
> > > + */
> > > +#define RPROC_SET_SHUTDOWN_ON_RELEASE _IOW(RPROC_MAGIC, 1, __s32)
> > > +
> > > +/*
> > > + * The RPROC_GET_SHUTDOWN_ON_RELEASE ioctl gets information about whether the automatic shutdown of
> > > + * a remote processor is enabled or disabled when the controlling userspace closes the char device
> > > + * interface.
> > > + *
> > > + * output parameter: integer
> > > + *   0             : automatic shutdown disable
> > > + *   other : automatic shutdown enable
> > > + */
> > > +#define RPROC_GET_SHUTDOWN_ON_RELEASE _IOR(RPROC_MAGIC, 2, __s32)
> > > +
> > > +#endif
> > > --
> > > Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> > > a Linux Foundation Collaborative Project
> > >